The present invention relates to an apparatus and method for removing samples of materials undergoing processing in a rotary kiln and more particularly to a system mounted on the kiln for removing materials from the kiln interior in a sealed condition.
In the course of operating a rotary kiln it is usually necessary to be able to take samples of the materials in the kiln during the process to evaluate process operation and performance. Since in many processes, such as the direct reduction of materials containing iron oxides, the kiln interior and the materials are very hot and the kiln is typically long and slender in construction, it is difficult to obtain material samples through ports or doors in the kiln ends, and since it is usually desirable to obtain samples from along the kiln length, a series of ports are conventionally formed in the kiln shell to permit withdrawal of the material samples. The closures for such ports, however, may cause problems, as they sometimes leak, spill the materials and are difficult to operate and maintain particularly in an industrial plant environment. Additionally, the material removing operation can result in contamination of the material sampled.
An example of one prior art sampling device is shown in U.S. Pat. No. 3,613,453 to Small et al and involves a sampling chamber communicating with the kiln interior and provided externally of the kiln with an inspection port, a temperature-sensing port and a material-removal port. The temperature-sensing and material-removal ports have automatically-operated pivotally mounted covers which open the sample chamber interior to the outside environment.
Another sampling device currently in use involves a sampling vessel or catch can which is attached to a gate device. The can and gate device are movable together into a position wherein an orifice in the gate device matches a sample orifice on the kiln shell permitting a sample of the material in the kiln to pass into the catch pan. The gate device is provided on one side with a hinge, having a spring loaded bolt to maintain the gate device in a sealing position, and on the other side with an operating arm which has a radius slot with a washer and spring assembly that assists the hinge bolt in maintaining the sealing. This arrangement has been found to leak material from the kiln, and occasional disconnecting of the catch can from the gate device results in spillage of material out of the kiln. Consequently, the device is unsafe and the leakage permits hot samples to interact with the outside environment causing contamination and/or chemical changes therein.
It is therefore desirable that a material sampling system for recovering samples of materials being processed in a rotary kiln be provided that will maintain sealing of the kiln and sampling system while operating easily and safely to remove samples, and additionally that will seal hot samples for a cooling period to avoid contamination or chemical change. The present invention provides such a sampling system of rugged construction and simple design with a minimum of moving parts and which maintains appropriate sealing of the kiln and sample.